Double eccentric valve

ABSTRACT

In a double eccentric valve, a valve seat or valve body includes a rubber seal part in which a seat surface or seal surface is formed. An interference between the valve seat and the valve body is made minimum at a position of a rotary-shaft-directional end of the valve body in the radial direction of the valve body which is parallel to an extending direction of the axis of a rotary shaft.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Division of U.S. application Ser. No. 16/613,232 filed on Nov.13, 2019, which is a National Stage Application of PCT InternationalPatent Application No. PCT/JP2018/021158 filed on Jun. 1, 2018, andclaiming the priority of Japanese Patent Applications No. 2017-135584filed on Jul. 11, 2017 and No. 2018-000908 filed on Jan. 8, 2018, theentire contents of which are herewith incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a double eccentric valve configuredsuch that a valve element is placed with its rotation center positionedeccentrically from a center of a valve hole of a valve seat, and asealing surface of the valve element is positioned eccentrically fromthe rotation center of the valve element.

BACKGROUND ART

As one conventional art, there is a double eccentric valve as disclosedin Patent document 1. This double eccentric valve is provided with avalve hole and a valve seat including an annular seat surface formedalong an edge of the valve hole, a valve element formed, on its outerperiphery, with an annular seal surface which faces the seat surface,and a rotary shaft for rotating the valve element. The axis (the centralaxis) of the rotary shaft extends in parallel with a radial direction ofthe valve element and the valve hole and is placed eccentrically in aradial direction of the valve hole from the center of the valve hole.The seal surface of the valve element is placed eccentrically from theaxis of the rotary shaft in a direction in which the axis of the valveelement extends. In the thus configured double eccentric valve, when thevalve element is rotated about the axis of the rotary shaft, the sealsurface is movable between a fully closed position at which the sealsurface is in surface contact with the seat surface and a fully openposition at which the seal surface is furthest away from the seatsurface.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: WO2016/002599A1

SUMMARY OF INVENTION Problems to be Solved by the Disclosure

When the foregoing double eccentric valve is provided with a rubber sealpart in the valve seat as a portion which can contact with the valveelement in order to enhance the sealing property (the sealing strength)between the valve seat and the valve element, a sliding resistance thatoccurs between the valve seat and the valve element during valveopening/closing operation may increase due to the frictional force ofthe rubber seal part. This may cause eccentrical abrasion of the rubberseal part, resulting in deterioration in durability of the rubber sealpart and thus the sealing property between the valve seat and the valveelement may deteriorate.

The present disclosure has been made in view of the circumstances tosolve the above problems and has a purpose to provide a double eccentricvalve capable of reducing sliding resistance which may occur between avalve seat and a valve element.

Means of Solving the Problems

To achieve the above purpose, one aspect of the disclosure provides adouble eccentric valve including: a valve seat including a valve holeand an annular seat surface formed along an edge of the valve hole; avalve element having a circular disc shape and including an outerperiphery formed with an annular seal surface corresponding to the seatsurface; and a rotary shaft configured to rotate the valve element, therotary shaft having an axis that extends in parallel with a radialdirection of the valve element and the valve hole, the rotary shaftbeing positioned eccentrically from a center of the valve hole in aradial direction of the valve hole, the seal surface being positionedeccentrically from the axis of the rotary shaft toward an extendingdirection of an axis of the valve element, and the valve element beingconfigured to rotate about the axis of the rotary shaft to move betweena fully closed position where the seal surface is in surface contactwith the seat surface and a fully open position where the seal surfaceis furthest away from the seat surface, wherein either the valve seat orthe valve element is provided with a rubber seal part formed with eitherthe seat surface or the seal surface, and the valve seat and the valveelement are configured to make an interference between the valve seatand the valve element minimum at a position of arotary-shaft-directional end of the valve element in the radialdirection of the valve element, which is a direction parallel to anextending direction of the axis of the rotary shaft.

The above aspect can reduce the interference between the valve seat andthe valve element at the position of a portion (i.e., therotary-shaft-directional end of the valve element) where the valveelement and the valve seat come in contact with each other for a longesttime during a valve opening/closing operation. This reduced interferenceresults in a reduced range of contact between the valve seat and thevalve element during the valve opening/closing operation. Accordingly,the sliding range of the valve seat and the valve element can bereduced, leading to a reduction in the sliding resistance which occursbetween the valve seat and the valve element.

In the foregoing aspect, preferably, the valve seat is provided with therubber seal part including the seat surface, and the valve element isprovided with a cutout portion at the position of therotary-shaft-directional end.

The foregoing aspect provided with the cutout portion can reduce theinterference with respect to the valve seat at the position of a portionof the valve element that contacts with the valve seat for a longesttime during a valve opening/closing operation. This reduced interferenceresults in a reduced area of contact with the valve seat during thevalve opening/closing operation. Accordingly, the sliding range of thevalve seat and the valve element can be reduced, leading to a reductionin the sliding resistance which occurs between the valve seat and thevalve element.

In the foregoing aspect, preferably, the valve element has an ellipticalshape with its minor axis extending in the direction parallel to theextending direction of the axis of the rotary shaft.

The foregoing aspect can gradually reduce the interference between thevalve seat and the valve element along a circumferential direction ofthe valve element, thereby further reducing the range of contact betweenthe valve seat and the valve element during the valve opening/closingoperation. Accordingly, the sliding range of the valve seat and thevalve element can be further reduced, leading to a reduction in thesliding resistance which occurs between the valve seat and the valveelement.

To achieve the aforementioned problems, another aspect of the presentdisclosure provides a double eccentric valve including: a valve seatincluding a valve hole and an annular seat surface formed along an edgeof the valve hole; a valve element having a circular disc shape andincluding an outer periphery formed with an annular seal surfacecorresponding to the seat surface; and a rotary shaft configured torotate the valve element, the rotary shaft having an axis that extendsin parallel with a radial direction of the valve element and the valvehole, the rotary shaft being positioned eccentrically from a center ofthe valve hole in a radial direction of the valve hole, the seal surfacebeing positioned eccentrically from the axis of the rotary shaft towardan extending direction of an axis of the valve element, and the valveelement being configured to rotate about the axis of the rotary shaft tomove between a fully closed position where the seal surface is insurface contact with the seat surface and a fully open position wherethe seal surface is furthest away from the seat surface,

wherein either the valve seat or the valve element is provided with arubber seal part formed with either the seat surface or the sealsurface, and the seat surface or the seal surface in the rubber sealpart includes a groove.

The above aspect can reduce the interference area of the rubber sealpart with respect to the valve element or the valve seat when the valveseat and the valve element contact each other. This configuration canreduce the repulsion force of the rubber seal part with respect to thevalve element or the valve seat, leading to a reduction in the slidingresistance which occurs between the valve seat and the valve elementwhile providing a sufficient sealing width between the valve seat andthe valve element.

In the foregoing aspect, preferably, the valve element includes a firstside part and a second side part divided by a boundary defined by avirtual plane extending from an axis of the rotary shaft in parallelwith an extending direction of the axis of the valve element, when thevalve element is rotated in a valve closing direction, the first sidepart rotates from an inside toward an outside of the valve hole whilethe second side part rotates from the outside toward the inside of thevalve hole, the rubber seal part is provided to the valve seat, thegroove extends entirely in a circumferential direction of the valveseat, and a portion of the groove located on a side where the first sidepart slides is placed at a position more inside the valve hole in adirection of a central axis of the valve hole relative to a portion ofthe groove located on a side where the second side part slides.

In the above aspect, the position of the groove varies with location inthe circumferential direction of the valve seat can reduce theinterference when the valve element and the rubber seal part of thevalve seat start to contact with each other during the valve closingoperation. In this manner, the above configuration can reduce thesliding resistance which occurs between the valve seat and the valveelement before the fully closed state is reached during the valveclosing operation. Even during a valve opening operation, the aboveconfiguration can reduce the sliding range of the valve seat and thevalve element, leading to a reduction in the sliding resistance whichoccurs between the valve seat and the valve element.

To achieve the aforementioned problems, another aspect of the presentdisclosure provides a double eccentric valve including: a valve seatincluding a valve hole and an annular seat surface formed along an edgeof the valve hole; a valve element having a circular disc shape andincluding an outer periphery formed with an annular seal surfacecorresponding to the seat surface; and a rotary shaft configured torotate the valve element, the rotary shaft having an axis that extendsin parallel with a radial direction of the valve element and the valvehole, the rotary shaft being positioned eccentrically from a center ofthe valve hole in a radial direction of the valve hole, the seal surfacebeing positioned eccentrically from the axis of the rotary shaft towardan extending direction of an axis of the valve element, and the valveelement being configured to rotate about the axis of the rotary shaft tomove between a fully closed position where the seal surface is insurface contact with the seat surface and a fully open position wherethe seal surface is furthest away from the seat surface,

wherein the valve element includes a first side part and a second sidepart divided by a boundary defined by a virtual plane extending from anaxis of the rotary shaft in parallel with an extending direction of theaxis of the valve element, when the valve element is rotated in a valveclosing direction, the first side part rotates from an inside toward anoutside of the valve hole while the second side part rotates from theoutside toward the inside of the valve hole, the valve element isprovided with a rubber seal part including the seal surface, and aportion of the rubber seal part located close to the second side part isconfigured to enter in the valve hole by a smaller amount during fullclosing than a portion of the rubber seal part located close to thefirst side part.

The foregoing aspect in which the rubber seal part can enter in thevalve hole by a reduced distance during full closing, so that the amountof contact of the rubber seal part with the valve seat is reduced.During a valve opening/closing operation, the above configuration canreduce the sliding range of the valve seat and the valve element. Thisenables a reduction in the sliding resistance which occurs between thevalve seat and the valve element.

In the foregoing aspect, preferably, the rubber seal part is attached toan outer periphery of the valve element in the radial direction so thata central axis of the rubber seal part is oblique to the axis of thevalve element, and a portion of the rubber seal part located close tothe second side part is formed at a position outside the valve holeduring full closing in a direction of the axis of the valve element thana portion of the rubber seal part located close to the first side part.

In the foregoing aspect, preferably, the rubber seal part is attached toan outer periphery of the valve element in the radial direction so thata central axis of the rubber seal part coincides with the axis of thevalve element, and a portion of the rubber seal part close to the secondside part is smaller in thickness in a direction of the central axis ofthe rubber seal part than a portion of the rubber seal part close to thefirst side part.

To achieve the aforementioned problems, another aspect of the presentdisclosure provides a double eccentric valve including: a valve seatincluding a valve hole and an annular seat surface formed along an edgeof the valve hole; a valve element having a circular disc shape andincluding an outer periphery formed with an annular seal surfacecorresponding to the seat surface; and a rotary shaft configured torotate the valve element, the rotary shaft having an axis that extendsin parallel with a radial direction of the valve element and the valvehole, the rotary shaft being positioned eccentrically from a center ofthe valve hole in a radial direction of the valve hole, the seal surfacebeing positioned eccentrically from the axis of the rotary shaft towardan extending direction of an axis of the valve element, and the valveelement being configured to rotate about the axis of the rotary shaft tomove between a fully closed position where the seal surface is insurface contact with the seat surface and a fully open position wherethe seal surface is furthest away from the seat surface,

wherein at least one of the seat surface and the seal surface includesan asperity or a groove.

The above aspect can reduce the area of contact between the valve seatand the valve element, leading to a reduction in the sliding resistancewhich occurs between the valve seat and the valve element.

In the foregoing aspect, preferably, either the valve seat or the valveelement is provided with a rubber seal part including the seat surfaceor the seal surface, and the seat surface or the seal surface of eitherone of the valve seat or the valve element, the one being not providedwith the rubber seal part, includes the asperity or the groove.

The above aspect in which either the valve seat or the valve element isprovided with the rubber seal part can reduce the area of contactbetween the valve seat and the valve element, leading to a reduction inthe sliding resistance which occurs between the valve seat and the valveelement.

In the foregoing aspect, preferably, the asperity or the groove isformed in larger numbers for a lower request value for slidingresistance of the valve element with respect to the valve seat.

The above aspect in which more numerous asperities or grooves are formedto reduce the area of contact between the valve seat and the valveelement can reduce the sliding resistance which occurs between the valveseat and the valve element.

In the foregoing aspect, preferably, the valve seat and the valveelement are configured to provide a linear contact area within a slidingregion of the valve seat and the valve element in a cross-section of thevalve seat and the valve element in an axial direction when the valveelement is in the fully closed position.

The above aspect in which a fluid is blocked off in a region where thevalve seat and the valve element are in linear contact with each otherin the fully closed state can prevent leakage of the fluid.

Effects of the Invention

A double eccentric valve of the present disclosure can reduce thesliding resistance which occurs between a valve seat and a valveelement.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing one example of a flow control valveprovided with a double eccentric valve of the present disclosure;

FIG. 2 is a perspective view showing a valve section in a fully closedstate including a partially cutaway view;

FIG. 3 is a perspective view showing the valve section in a fully openstate including the partially cutaway view;

FIG. 4 is a side view showing a valve seat, a valve element, and arotary shaft in a valve closed state;

FIG. 5 is a A-A cross-sectional view in FIG. 4 ;

FIG. 6 is a cross-sectional view showing the valve seat and the valveelement in a fully closed state;

FIG. 7 is a plan view of the valve seat and the valve element in thefully closed state;

FIG. 8 is a plan view of the valve element in a first embodiment;

FIG. 9 is a B-B cross-sectional view in FIG. 8 ;

FIG. 10 is a diagram showing an interference with respect to the valveseat at each valve position in the first embodiment;

FIG. 11 is a plan view of a valve element in a second embodiment;

FIG. 12 is a diagram showing an interference with respect to a valveseat at each valve position in the second embodiment;

FIG. 13 is a diagram showing an example that the valve element isprovided with a rubber seal part;

FIG. 14 is a view corresponding to a C-C cross-section and a D-Dcross-section in FIG. 7 in Example 1 of a third embodiment;

FIG. 15 is a view showing changes in magnitude of torque of a rotaryshaft in Example 1 of the third embodiment;

FIG. 16 is a schematic perspective view of a valve seat in Example 2 ofthe third embodiment, showing that the position of a groove varies withlocation in a circumferential direction of the valve seat;

FIG. 17 is a view corresponding to the C-C cross-section and the D-Dcross-section in FIG. 7 in Example 2 of the third embodiment;

FIG. 18 is a side view of a valve element in a fourth embodiment;

FIG. 19 is a cross-sectional view of the valve element and a valve seatduring full closing in the fourth embodiment;

FIG. 20 is a side view of a valve element in a fifth embodiment;

FIG. 21 is a cross-sectional view of the valve element and a valve seatduring full closing in the fifth embodiment;

FIG. 22 is a cross-sectional view corresponding to the C-C cross sectionin FIG. 7 , in which the valve element is illustrated in an externalview, in Example 1 of a sixth embodiment;

FIG. 23 is a graph showing peak torques obtained when shot blast hasbeen executed and when shot blast has not been executed;

FIG. 24 is a cross-sectional view corresponding to the C-C cross sectionin FIG. 7 , in which the valve element is illustrated in an externalview, in Example 2 of a sixth embodiment;

FIG. 25 is an enlarged cross-sectional view corresponding to the C-Ccross-section in FIG. 7 in Example 3 of the sixth embodiment;

FIG. 26 is a view showing a variation example of Example 3 of the sixthembodiment; and

FIG. 27 is a diagram showing an interference with respect to a valveseat at each valve position in a comparison embodiment.

MODE FOR CARRYING OUT THE INVENTION

A detailed description of a preferred embodiment of a double eccentricvalve of the present disclosure embodied in a flow control valve willnow be given referring to the accompanying drawings.

First Embodiment

A first embodiment will be first described. As shown in FIG. 1 , a flowcontrol valve 1 includes a valve section 2 made up of a double eccentricvalve, a motor section 3 including a built-in motor, and aspeed-reducing mechanical section 4 including a plurality of gears builttherein. As shown in FIGS. 2 and 3 , the valve section 2 includes a pipepart 12 made of metal having a flow passage 11 in which a fluid flows.In this flow passage, a valve seat 13, a valve element 14, and a rotaryshaft 15 are placed. The inner shape of the flow passage 11, the outershape of the valve seat 13, and the outer shape of the valve element 14are each circular or nearly circular in plan view. The rotary shaft 15is arranged to receive the torque of the motor via the plurality ofgears. In the present embodiment, the pipe part 12 having the flowpassage 11 corresponds to a part of a housing 6. This housing 6 coversthe motor of the motor section 3 and the plurality of gears of thespeed-reducing mechanism section 4. The housing 6 is made of metal, suchas aluminum.

The flow passage 11 is formed with a step portion 10, on which the valveseat 13 is mounted. The valve seat 13 has an annular shape and includesa circular or nearly circular valve hole 16 at the center. The valvehole 16 is formed, along its edge, with an annular seat surface 17. Inthe present embodiment, the valve seat 13 is provided with a rubber sealpart 13 a in which the seat surface 17 is formed. The valve element 14has a circular-disk shape and includes an outer periphery formed with anannular seal surface 18 corresponding to the seat surface 17. The valveelement 14 is fixed to the rotary shaft 15 and rotatable together withthe rotary shaft 15.

As shown in FIGS. 5 to 7 , an axis L1 of the rotary shaft 15 extends inparallel with a radial direction of the valve element 14 and a radialdirection of the valve hole 16 and is placed eccentrically in a radialdirection of the valve hole 16 from the center P1 of the valve hole 16.The seal surface 18 of the valve element 14 is placed eccentrically fromthe axis L1 of the rotary shaft 15 toward an extending direction of anaxis L2 of the valve element 14. When the valve element 14 is rotatedabout the axis L1 of the rotary shaft 15, the seal surface 18 of thevalve element 14 is movable between a fully closed position (see FIG. 2) where the seal surface 18 is in surface contact with the seat surface17 of the valve seat 13 and a fully open position (see FIG. 3 ) wherethe seal surface 18 is furthest away from the seat surface 17.

In the present embodiment, in FIG. 5 , when the valve element 14 startsto rotate in a valve opening direction (a direction indicated by arrowsF1 in FIG. 5 , that is, a clockwise direction in FIG. 5 ) from the fullyclosed position, the seal surface 18 of the valve element 14simultaneously starts to separate from the seat surface 17 and movealong rotational paths T1 and T2 about the axis L1 of the rotary shaft15.

As shown in FIGS. 6 and 7 , the valve element 14 is divided into twoportions, i.e., a first side part 21 (a shaded area in FIGS. 6 and 7 )and a second side part 22 (an unshaded area in FIGS. 6 and 7 ) by aboundary defined by a virtual plane V1 extending from the axis L1 of therotary shaft 15 and in parallel with an extending direction of a centralaxis L3 of the valve hole 16 (the axis L2 of the valve element 14). Whenthe valve element 14 is rotated in the valve opening direction indicatedby the arrows F1 from the fully closed position shown in FIG. 6 , thefirst side part 21 rotates toward the inside of the valve hole 16 andthe second side part 22 rotates toward the outside of the valve hole 16.When the valve element 14 is rotated in the valve closing direction (anopposite direction to the direction indicated by the arrows F1) from thevalve open position (see FIG. 3 ) toward the fully closed position shownin FIG. 6 , the first side part 21 rotates from the inside toward theoutside of the valve hole 16 and the second side part 22 rotates fromthe outside toward the inside of the valve hole 16.

As shown in FIGS. 4 to 7 , the valve element 14 includes a fixed portion14 b having a mountain-like shape that protrudes from a plate surface 14a on an upper side of the valve element 14 and is fixed to the rotaryshaft 15. This fixed portion 14 b is fixed to the rotary shaft 15through a pin 15 a protruding from a distal end of the rotary shaft 15and at a position displaced in the radial direction of the rotary shaft15 from the axis L1 of the rotary shaft 15. As shown in FIGS. 5 to 7 ,furthermore, the fixed portion 14 b is placed on the axis L2 of thevalve element 14 and the valve element 14 including the fixed portion 14b has a bilaterally symmetrical shape relative to the axis L2 of thevalve element 14.

In the present embodiment, an end face of the valve element 14 is cutaway. Specifically, as shown in FIGS. 8 and 9 , the valve element 14 isprovided with a cut portion 31 (a cutout portion) at a position (a valveposition PO5) of each end (a rotary-shaft-directional end) of the valveelement 14 in the radial direction thereof, which is a directionparallel to the extending direction of the axis L1 of the rotary shaft15. This valve element 14 is cut away at both end faces in the axis L1direction of the rotary shaft 15 (a vertical direction in FIG. 8 ). Sucha valve element 14 has a perfect circular shape with bothradial-direction ends cut away. In one example, in which the diameter ofthe valve element 14 is 30 mm, the maximum cut width of the valveelement 14 in the radial direction at each cut portion 31 is set to 0.05mm.

The above configuration makes an interference TM between the valve seat13 (specifically, the rubber seal part 13 a) and the valve element 14(hereinafter, simply referred to as an “interference TM”) minimum at thevalve position PO5. Specifically, as shown in FIG. 10 , the interferenceTM (indicated by a dotted line in FIG. 10 ) at the valve position PO5 issmaller than interferences TM (indicated by solid lines in FIG. 10 ) atvalve positions PO1, PO2, PO3, and PO4 (see FIG. 8 ).

Herein, the valve position PO1 is a position of an end of the valveelement 14 in a radial direction thereof corresponding to a directionperpendicular to the extending direction of the axis L1 of the rotaryshaft 15, as shown in FIG. 8 . The valve position PO5 is a position ofan end of the valve element 14 in the radial direction thereofcorresponding to a direction parallel to the extending direction of theaxis L1 of the rotary shaft 15. The valve positions PO2, PO3, and PO4are positions displaced from one another in a circumferential directionof the valve element 14 between the valve position PO1 and the valveposition PO5.

In the present embodiment described as above, the valve element 14 isprovided with the cut portion 31, thereby reducing the interference TMat a position (the valve position PO5) of a contact portion (therotary-shaft-directional end of the valve element 14) where the valveelement 14 and the valve seat 13 contact with each other for a longesttime during valve opening/closing operation. This reduced interferenceTM can result in a reduced range of contact between the valve seat 13and the valve element 14 during valve opening/closing operation.Accordingly, a sliding range of the valve seat 13 and the valve element14 can be reduced, leading to a reduction in sliding resistance whichoccurs between the valve seat 13 and the valve element 14.

In a comparative embodiment in which a valve element 14 does not includea cut portion 31 as shown in FIG. 27 , an interference TM at a valveposition PO5 is made large and thus a whole-circumferential-open openingdegree becomes large. In the first embodiment, however, the interferenceTM at the valve position PO5 is small as shown in FIG. 10 as comparedwith that in the comparative Example and therefore thewhole-circumferential-open opening degree becomes small. Thiswhole-circumferential-open opening degree represents an opening degreewhen an interference TM is 0 because the valve element 14 does notcontact, over its entire circumference, with the valve seat 13.

Second Embodiment

Second through sixth embodiments will be described below, in whichsimilar or identical parts or components to those in the firstembodiment are assigned the same reference signs as in the firstembodiment and their details are not elaborated upon here. The followingdescription will be given with a focus on differences from the firstembodiment. First, the second embodiment will be described below.

In the present embodiment, the valve element 14 has an elliptical shapewith its minor axis extending in a direction parallel to the extendingdirection of the axis L1 of the rotary shaft 15 as shown in FIG. 11 .

As shown in FIG. 12 , the interference TM is thus gradually smaller atthe valve positions PO1, PO2, PO3, PO4, and PO5 in this order. Theinterference TM is made minimum at the valve position PO5. As oneexample, during full closing (the opening degree is 0), the interferenceTM at the valve position PO5 is smaller by 0.05 mm than the interferenceTM for the valve element 14 having a perfect circular shape.

In the present embodiment, therefore, the interference TM can be setgradually smaller from the valve position PO1 toward the valve positionPO5 along the circumferential direction of the valve element 14, so thatthe range of contact between the valve seat 13 and the valve element 14during the valve opening/closing operation can be reduced from the valveposition PO2 to the valve position PO5. This configuration can furtherreduce the sliding range of the valve seat 13 and the valve element 14,thereby enabling reduction in the sliding resistance which occursbetween the valve seat 13 and the valve element 14.

In the present embodiment, furthermore, the interference TM at each ofthe valve positions PO1, PO2, PO3, PO4, and PO5 as shown in FIG. 12 issmaller than that in the comparative Example shown in FIG. 27 . Thus,the whole-circumferential-open opening degree can be further reduced.

As an alternative, as shown in FIG. 13 , the valve element 14 may beprovided with a rubber seal part 14 c, instead the valve seat 13 beingprovided with the rubber seal part 13 a. In this case, the rubber sealpart 14 c includes the seal surface 18. Accordingly, the pipe section 12(a body) and the valve seat 13 can be integrally molded. Thisconfiguration eliminates the need for mounting the valve seat 13 bypress-fit into the pipe section 12 (the step portion 10) and hence savesthe trouble of positioning the valve seat 13, resulting in costreduction. Further, this configuration is free from the risk that afluid leaks from a portion on which the valve seat 13 is mounted.

In the present embodiment, as a variation example, the valve element 14may be further provided with a cutout portion as with the cut portion 31in the first embodiment.

Third Embodiment

A third embodiment will be described hereinafter.

Example 1

First, Example 1 of the third embodiment will be described below. Inthis example, the rubber seal part 13 a of the valve seat 13 isadditionally provided with a groove 32 in a portion that will interactor interfere with the valve element 14. Specifically, as shown in FIG.14 , the groove 32 is formed in the seat surface 17 of the rubber sealpart 13 a of the valve seat 13. The groove 32 in the present exampleextends entirely in the circumferential direction of the valve seat 13.This groove 32 is located, entirely in the circumferential direction ofthe valve seat 13, at the same position in the direction of the centralaxis L3 of the valve hole 16.

This configuration can reduce the interference area S (see FIG. 14 ) ofthe rubber seal part 13 a of the valve seat 13 with respect to the valveelement 14 when the valve seat 13 and the valve element 14 contact eachother. This can reduce the repulsive force of the rubber seal part 13 aof the valve seat 13 to the valve element 14, leading to a reduction insliding resistance which occurs between the valve seat 13 and the valveelement 14. Such a configuration can reduce a peak torque (a maximumtorque) of the rotary shaft 15 during a valve opening operation shown inFIG. 15 (“Toward Open” in the figure), leading to a reduction in slidingresistance which occurs between the valve seat 13 and the valve element14. A sealing width δ of the valve seat 13 and the valve element 14 isensured.

The valve element 14 may be provided with a rubber seal part instead ofthe valve seat 13 being provided with the rubber seal part 13 a, and aseal surface 18 of this rubber seal part of the valve element 14 may beformed with the groove 32. As an alternative, the groove 32 may be onlyformed partially in the circumferential direction of either the valveseat 13 or the valve element 14. As another alternative, a flat portion34 may be provided within a sliding region SA of the valve seat 13 andthe valve element 14, as shown in FIG. 24 which will be described later.

Example 2

Example 2 of the third embodiment will be described below. In thisexample, the position of the groove 32 varies with location in thecircumferential direction of the valve seat 13. Specifically, the groove32 extends entirely in the circumferential direction of the valve seat13 as shown in FIGS. 16 and 17 . A first portion 32 a of the groove 32,located on a side where the first side part 21 of the valve element 14slides, is placed at a position more inside the valve hole 16 (a lowerside in FIG. 17 , which is a side apart from the rotary shaft 15) in thecentral axis L3 of the valve hole 16 than a second portion 32 b (locatedat a position indicated by a dashed-dotted line in FIG. 17 ) located ona side where the second side part 22 of the valve element 14 slides.

The position of the groove 32 varies with location in thecircumferential direction of the valve seat 13 as described above.Accordingly, when the valve element 14 moves in a direction indicated byarrows F2 during the valve closing operation and the valve element 14starts to contact with the rubber seal part 13 a of the valve seat 13,the interference TM can be small. Specifically, at the time when thevalve element 14 starts to contact with the rubber seal part 13 a asindicated by solid lines in FIG. 17 , the valve element 14 does notcontact with the rubber seal part 13 a at the first portion 32 a of thegroove 32, the interference TM can be small. Subsequently, a necessaryinterference TM can be obtained as indicated by a dashed-two dotted linein FIG. 17 during full closing. Thus, during valve closing operation,the sliding resistance which occurs between the valve seat 13 and thevalve element 14 can be reduced before the fully closed state isreached. Even during valve opening operation, the sliding range of thevalve seat 13 and the valve element 14 can be reduced, leading to areduction in the sliding resistance which occurs between the valve seat13 and the valve element 14.

The present example, as with the foregoing Example 1, can reduce thepeak torque of the rotary shaft 15 and thus reduce the slidingresistance which occurs between the valve seat 13 and the valve element14.

Fourth Embodiment

A fourth embodiment will be described below. In this embodiment, thevalve element 14 is provided with a rubber seal part 14 d on an outerperiphery of the valve element 14 in its radial direction as shown inFIG. 18 . This rubber seal part 14 d includes the seal surface 18. Therubber seal part 14 d is obliquely attached to the valve element 14.Specifically, the rubber seal part 14 d is attached on the outerperiphery of the valve element 14 in its radial direction so that acentral axis L4 of the rubber seal part 14 d is oblique (at a slant) tothe axis L2 of the valve element 14. The thickness of the rubber sealpart 14 d is constant over the circumferential direction of the rubberseal part 14 d. Furthermore, as shown in FIG. 19 , a second portion 14db of the rubber seal part 14 d, located on a side close to the secondside part 22 of the valve element 14, is placed at a position moreoutside in the valve hole 16 (the upper side in FIG. 19 ) in thedirection of the axis L2 of the valve element 14 than a first portion 14da of the rubber seal part 14 d located on a side close to the firstside part 21 of the valve element 14.

As shown in FIG. 19 , the second portion 14 db in the rubber seal part14 d configured as above enters into the valve hole 16 by a smalleramount during full closing is smaller than the first portion 14 da ofthe rubber seal part 14 d, and thus contacts with the valve seat 13 in asmaller amount during full closing than the first portion 14 da. Duringvalve opening/closing operation, the sliding range of the valve seat 13and the valve element 14 (particularly, the sliding range of the valveseat 13 and the second portion 14 db of the rubber seal part 14 d) canbe reduced. This enables a reduction in the sliding resistance whichoccurs between the valve seat 13 and the valve element 14.

Fifth Embodiment

A fifth embodiment will be described below. In this embodiment, thevalve element 14 is provided with a rubber seal part 14 e on an outerperiphery of the valve element 14 in its radial direction as shown inFIG. 20 . This rubber seal part 14 e includes the seal surface 18. Therubber seal part 14 e is attached to the outer periphery of the valveelement 14 in its radial direction so that the central axis L5 of therubber seal part 14 e coincides with the axis L2 of the valve element14. The rubber seal part 14 e has a thickness that is thin on one sideand thick on the other side. Specifically, a second portion 14 eb of therubber seal part 14 e located on the side close to the second side part22 is smaller in thickness in the central axis L5 of the rubber sealpart 14 e than a first portion 14 ea of the rubber seal part 14 elocated on the side close to the first side part 21.

As shown in FIG. 21 , the second portion 14 eb of the rubber seal part14 e configured as above enters in the valve hole 16 by a smaller amountduring full closing than the first portion 14 ea of the rubber seal part14 e, and thus contacts with the valve seat 13 in a smaller area duringfull closing. During valve opening/closing operation, the sliding rangeof the valve seat 13 and the valve element 14 (particularly, the slidingrange of the valve seat 13 and the second portion 14 eb of the rubberseal part 14 e) can be reduced. This enables a reduction in the slidingresistance which occurs between the valve seat 13 and the valve element14.

Sixth Embodiment

A sixth embodiment will be described hereinafter.

Example 1

First, Example 1 of the sixth embodiment will be described below. Inthis example, for the valve seat 13 provided with the rubber seal part13 a, the valve element 14 made of metal (e.g., stainless steel)provided with no rubber seal part is formed with asperities including aplurality of (countless) pits 33 formed on the seal surface 18 as shownin FIG. 22 . The asperities (the pits 33) are made for example by shotblast applied to the outer peripheral surface of the valve element 14.This configuration can reduce the area of contact between the valve seat13 and the valve element 14 in the fully closed state.

An analysis result of the present example reveals, as shown in FIG. 23 ,that a peak torque PT of the outer peripheral surface of the valveelement 14 that was subjected to shot blast (the case of “Shot blastexecuted”) becomes lower than a peak torque PT of the outer peripheralsurface of the valve element 14 that was not subjected to shot blast(the case of “Shot blast unexecuted”). Since the seal surface 18 isformed with asperities by shot blast applied to the outer peripheralsurface of the valve element 14, the peak torque PT can be reduced,leading to a reduction in the sliding resistance which occurs betweenthe valve seat 13 and the valve element 14.

According to the present example described above, when the valve seat 13is provided with the rubber seal part 13 a, the metal valve element 14provided with no rubber seal part is formed with the asperities on theseal surface 18.

This configuration can reduce the contact area between the valve seat 13and the valve element 14 without changing the sealing width δ and theinterference TM. This leads to a reduction in the sliding resistancewhich occurs between the valve seat 13 and the valve element 14.

As the request value for the sliding resistance of the valve element 14to the valve seat 13 is lower (i.e., as the request for reducing thesliding resistance is stricter), more numerous asperities may be formed.

As a variation example, when the valve element 14 is provided with therubber seal part, the valve seat 13 made of metal (e.g., aluminum)provided with no rubber seal part may be formed with the asperities onthe seat surface 17. As another variation example, the valve seat 13 orthe valve element 14 may be formed with the asperities only on the seatsurface 17 or the seal surface 18 instead of over the whole outerperipheral surface of the valve seat 13 or the valve element 14.

Example 2

Example 2 of the sixth embodiment will be described below with a focuson differences of Example 1 of the sixth embodiment. In the presentexample, the valve element 14 is formed with the asperities on the sealsurface 18 and a part of the seal surface 18 is formed with a flatportion 34 as shown in FIG. 24 . Specifically, in axial cross-sectionsof the valve seat 13 and the valve element 14 (a cross-section takenalong an axial direction) while the valve element 14 is in the fullyclosed position (in the fully closed state), the flat portion 34 isprovided within a sliding region SA of the valve seat 13 and the valveelement 14 as a region where the valve seat 13 and the valve element 14come into linear contact with each other. Such a flat portion 34 isformed entirely in the circumferential direction of the valve element14. This flat portion 34 can keep the sealing strength in the fullyclosed state. As a variation example, the valve seat 13 is formed withthe asperities on the seat surface 17, a part of this seat surface 17may be formed with the flat portion 34.

According to the present example described above, in axialcross-sections of the valve seat 13 and the valve element 14 in thefully closed state, the flat portion 34 is provided within the slidingregion SA of the valve seat 13 and the valve element 14 as a regionwhere the valve seat 13 and the valve element 14 come into linearcontact with each other. In the fully closed state, accordingly, a fluidis blocked off by the flat portion 34 and thus can be prevented fromleaking.

Example 3

Further, Example 3 of the sixth embodiment will be described below. Inthis example, when the valve seat 13 is provided with the rubber sealpart 13 a, the metal valve element 14 provided with no rubber seal partis formed with two grooves 35 on the seal surface 18 as shown in FIG. 25. These grooves 35 are formed extending entirely in the circumferentialdirection of the valve element 14.

Such a seal surface 18 formed with the two grooves 35 provides a lowerrepulsive force than the seal surface 18 not formed with the grooves 35.

The number of grooves 35 is not particularly limited and, for example,four grooves 35 may be formed on the seal surface 18 as a variationexample shown in FIG. 26 . This allows a reduction in the contact areabetween the valve seat 13 and the valve element 14 as compared with theseal surface 18 formed with two grooves 35. Thus, for example, it may bearranged such that two grooves 35 are formed on the seal surface 18 togive priority to enhancement of the sealing strength in the fully closedstate, whereas four grooves 35 are formed on the seal surface 18 to givepriority to reduction in the sliding resistance which occurs between thevalve seat 13 and the valve element 14. That is, more numerous grooves35 may be formed for a lower request value for the sliding resistance ofthe valve element 14 with respect to the valve seat 13.

According to the present example configured as above, when the valveseat 13 is provided with the rubber seal part 13 a, the metal valveelement 14 provided with no rubber seal part is formed with the grooves35 on the seal surface 18.

This configuration can reduce the contact area between the valve seat 13and the valve element 14 without changing the sealing width _δ and theinterference TM, leading to a reduction in the sliding resistance whichoccurs between the valve seat 13 and the valve element 14. For a rubberseal part formed with a groove(s), the accuracy of forming the groove(s)may be an issue. In the present example, however, the grooves 35 areformed on the seal surface 18 of the metal valve element 14, theaccuracy of forming the grooves 35 can be enhanced.

As an alternative, more numerous grooves 35 may be formed for a lowerrequest value for the sliding resistance of the valve element 14 withrespect to the valve seat 13. When the grooves 35 are formed in largenumbers to reduce the contact area between the valve seat 13 and thevalve element 14 as above, the sliding resistance which occurs betweenthe valve seat 13 and the valve element 14 can be reduced.

As a variation example, when the valve element 14 is provided with therubber seal part, the metal valve seat 13 provided with no rubber sealpart may include the groove(s) 35 on the seat surface 17. As anothervariation, the groove(s) 35 may be only formed partially in thecircumferential direction of the valve seat 13 or valve element 14. Theflat portion 34 (see FIG. 24 ) may be provided within the sliding regionSA of the valve seat 13 and the valve element 14.

The foregoing embodiments are mere examples and give no limitations tothe present disclosure. The present disclosure may be embodied in otherspecific forms without departing from the essential characteristicsthereof.

For instance, the seat surface 17 of the valve seat 13 and the sealsurface 18 of the valve element 14 may both be formed with a groove orgrooves. Further, both the valve element 14 and the valve seat 13 may beprovided with a rubber seal part. Alternatively, neither the valveelement 14 nor the valve seat 13 may be provided with a rubber sealpart. As an alternative, the seat surface 17 of the metal valve seat 13or the seal surface 18 of the metal valve element 14, each including norubber seal part, may be formed with both the asperities and thegroove(s) 35.

REFERENCE SIGNS LIST

-   1 Flow control valve-   2 Valve section-   3 Motor section-   13 Valve seat-   13 a Rubber seal part-   14 Valve element-   14 c Rubber seal part-   14 d Rubber seal part-   14 da First portion-   14 db Second portion-   14 e Rubber seal part-   14 ea First portion-   14 eb Second portion-   15 Rotary shaft-   15 a Pin-   16 Valve hole-   17 Seat surface-   18 Seal surface-   21 First side part-   22 Second side part-   31 Cut portion-   32 Groove-   32 a First portion-   32 b Second portion-   33 Pit-   34 Flat portion-   35 Groove-   L1 Axis (of rotary shaft)-   L2 Axis (of valve element)-   L3 Central axis (of valve hole)-   L4 Central axis (of rubber seal part)-   L5 Central axis (of rubber seal part)-   V1 Virtual plane-   PO1, PO2, PO3, PO4, PO5 Valve position-   TM Interference-   S Interference area-   PT Peak torque-   δ Sealing width-   SA Sliding region

The invention claimed is:
 1. A double eccentric valve comprising: avalve seat including a valve hole and an annular seat surface formedalong an edge of the valve hole; a valve element having a circular discshape and including an outer periphery formed with an annular sealsurface corresponding to the seat surface; and a rotary shaft configuredto rotate the valve element, the rotary shaft having an axis thatextends in parallel with a radial direction of the valve element and thevalve hole, the rotary shaft being positioned eccentrically from acenter of the valve hole in a radial direction of the valve hole, theseal surface being positioned eccentrically from the axis of the rotaryshaft toward an extending direction of an axis of the valve element, andthe valve element being configured to rotate about the axis of therotary shaft to move between a fully closed position where the sealsurface is in surface contact with the seat surface and a fully openposition where the seal surface is furthest away from the seat surface,wherein the valve element includes a first side part and a second sidepart divided by a boundary defined by a virtual plane extending from theaxis of the rotary shaft in parallel with an extending direction of theaxis of the valve element, when the valve element is rotated in a valveclosing direction, the first side part rotates from an inside toward anoutside of the valve hole while the second side part rotates from theoutside toward the inside of the valve hole, the valve element isprovided with a rubber seal part including the seal surface, a portionof the rubber seal part located close to the second side part isconfigured to enter in the valve hole by a smaller amount during fullclosing than a portion of the rubber seal part located close to thefirst side part, the rubber seal part is attached to an outer peripheryof the valve element in the radial direction so that a central axis ofthe rubber seal part is oblique to the axis of the valve element, and aportion of the rubber seal part located close to the second side part isformed at a position more outside in the valve hole during full closingin a direction of the axis of the valve element than a portion of therubber seal part located close to the first side part.